Prior art balers generally have a bale forming chamber defined by an apron comprising an array of side-by-side belts, transverse slats trained on chains, a plurality of rolls or a combination of these various elements, e.g., rolls and belts. Crop material, such as hay, is picked up from the ground as the baler traverses the field, fed into a fixed or variable chamber where it is accumulated and compressed to form a cylindrical package of crop material. The formed package, while in its compacted condition inside the chamber, is wrapped with net, plastic film, twine or the like, to produce a completed round bale that is then ejected from the chamber onto the ground for subsequent handling.
Exemplary of prior art round balers of the type referred to above having a fixed chamber, i.e., a bale forming chamber that does not vary in size, are the various balers disclosed in U.S. Pat. Nos. 4,176,596, issued Dec. 4, 1979 in the name of Hans O. Sacht, 4,212,149, issued Jul. 15, 1980 in the name of Bernard Krone et al, and 4,599,844, issued Jul. 15, 1986 in the name of Gerhard Clostermeyer et al, each of which illustrates a different type of apron assembly. In U.S. Pat. No. 4,176,596 a baler is disclosed in which the bale forming chamber is defined by a plurality of similar groups of side-by-side conveyor belts arranged around the periphery of the chamber. The conveyor comprises a pair of opposing chains between which a plurality of parallel crop engaging slats are mounted. The chamber in U.S. Pat. No. 4,212,149 is defined by a continuous slatted conveyor in combinations with a pair of floor rolls, in which an inner run of the conveyor is guided along a fixed path along a major portion of the periphery of the chamber. A third type of apron assembly, shown in U.S. Pat. No. 4,599,844, consists of a plurality of adjacent rolls arranged transversely in a generally circular array to define a cylindrical chamber.
Various wrapping systems employ known wrapping materials, such as net or twine, to wrap compacted packages of crop material formed in round balers. For example, the Sacht and Krone et al patents, mentioned above, refer to commonly accepted twine wrapping systems for completing bales formed in fixed chamber balers. In another patent, also directed to a fixed chamber round baler, where the chamber is defined by transverse slats mounted on chains, U.S. Pat. No. 4,610,123, issued Sep. 9, 1986 in the name of Bernard Krone et al, a net wrapping system is disclosed. In this baler the net is introduced into the fixed chamber via the transverse inlet through which crop material is fed. In still another fixed chamber baler patent, U.S. Pat. No. 5,231,828, issued Aug. 3, 1993 in the name of John R. Swearingen et al, a wrapping system is disclosed in which net, twine or plastic can be separately applied to a completed cylindrical package via the crop inlet.
In the wrapping system disclosed in the Clostermeyer et al patent, mentioned above, net is introduced into the forming chamber via a path between a pair of adjacent rolls in the circular array defining the chamber. Another example of this is illustrated in U.S. Pat. No. 4,580,398, issued Apr. 8, 1996 in the name of Dirk Bruer et al.
Although both twine wrapped and net wrapped bales are common and readily acceptable, many farmers prefer to use net for various reasons, e.g., less losses in certain crop conditions, a smoother outer surface on the completed bale which gives added protection against rain, and reduced field time for wrapping due to the reduced number of revolutions of the completed package in comparison to twine wrapping. Regardless of the wrapping medium, in a fixed chamber baler, as in most variable chamber balers, initiation of the wrapping step is not commenced until a cylindrical package of crop material has been fully formed and compacted in the chamber at which time the tail of the twine or net is introduced to the chamber between the forming elements of the apron or through the crop inlet. The twine or net is retained between the outer surface of the compacted cylindrical package of crop material and the apron, and due to frictional force the wrapping material encases or encircles the package as it continues to rotate in the chamber. Finally, the wrapping process is completed, the net or twine is severed, and a completed bale is discharged from the chamber.
As mentioned above one of the principal advantages of net wrapping is the ability to reduce wrapping time. This is accomplished by limiting the number of revolutions of the completed package in the chamber during wrapping which is a significant contribution to reduction of the overall elapsed time in the bale forming process as compared to twine where ten times that number would not be uncommon, depending on crop material and bale size. However, in some crop conditions, achieving this advantage, along with the other important advantages of net wrapped bales, is impacted by the necessity to wrap twine around a net wrapped bale to hold the net in place. This type of dual wrapping operation is especially prevalent when baling moist slippery crop material such as silage. In known apparatus, a common approach is the utilization of a subsequent, time consuming twine wrapping operation, i.e., additional revolutions of the completed bale either in the chamber or after discharge, requiring the attendant expenditure of time and effort.